The present invention relates to a character wheel used for a numbering machine, a data printing stamp, or other type of printing device and a method of manufacturing the same and also relates to a character wheel band or a character wheel ring usable for the character wheel and a method of manufacturing the same.
Numbering machines been extensively used as printing devices for numbering business documents or other documents to be printed. A conventional numbering machine includes a character wheel unit in a frame-shaped numbering main body such that it may move up and down. Desired printing element (portion) surfaces are selected from the character wheels of individual digits constituting the character wheel unit, and the surfaces of the selected printing portions are pressed against a document to number the same.
The character wheels of the respective digits constituting the character wheel unit are each formed by integrally molding the entire character wheels including the printing portions through a die casting process as disclosed in Japanese Utility Model Laid-open Publication No. SHO 62-15961, or by winding a flexible character wheel band around the outer periphery of a character wheel disc and fixing it by locking both ends of the flexible character wheel band in a locking groove provided in the space of a printing portion (element) mounting surface for one character formed on the outer peripheral surface of the character wheel disc as disclosed in Japanese Utility Model Laid-open Publication No. SHO 57-167869 or Japanese Utility Model Laid-open Publication No. SHO 58-69446.
In the former case where the character wheels of the respective digits constituting the character wheel unit are formed into one piece by the die casting, the one-piece molding formed through the die casting employs a metallic material such as aluminum, zinc, or iron, or a plastic material. The character wheels made of a metallic material or the like are plated with nickel, chromium, or the like which exhibits poor affinity for ink and high water repellency. This has been posing a problem in that ink is repelled or splashed, making it impossible to apply ink uniformly on a printing surface with a resultant blurred printed characters. Thus, uniformly printed sharp, clear characters have not been accomplished.
In the latter case where the flexible character wheel band is wound around the outer periphery of the character wheel disc and both ends thereof are fixed using the securing member, the locking groove is provided by utilizing the space for one character on the printing portion mounting surface of the outer peripheral surface of the character wheel disc, and the independent retaining member is used with the locking groove in order to fix both ends of the flexible character band. The locking groove, which occupies the space for one character, has been making it inappropriate for the numbering device adapted to print characters by successively rotating the character wheel band in turn.
Further, as the number of parts increases, it becomes difficult to maintain the accuracy of mounting the flexible character wheel band on the character wheel disc, so that it takes more time and effort to assemble the character wheel. In addition, since the flexible character wheel band is secured using the retaining member, the pitch of the printing blocks formed on the flexible character wheel band fails to be regular at the portion where the retaining member is attached, thus causing inconvenient variations in pitch. The flexible character wheel bands are formed by cutting the character wheel plate, which has been formed by vulcanizing, into narrow strips. It is difficult to insert a cutter between the flexible character wheel bands of the character wheel plate to accurately cut the flexible print bands with a precise width. Therefore, great care and effort have been required in cutting the character wheel plate, the cut flexible character wheel bands vary in width, and the variations are great, leading to such shortcomings as a low yield.
Moreover, the ends of the flexible character wheel bands are fixed by using the retaining members, making them impossible to be used as the character wheels for a numbering machine.